Some games use custom installers that do not provide an entry in the Add & Remove programs section when the actual installation is performed. Because of that, you are forced to use a 3rd party application which detects uninstallers and installed applications. In this case, a good approach is Your Uninstaller! because it has an "aggressive" way of detecting and removing applications that refuse to uninstall or don't have an uninstaller at all.
You can download and install the application from the Software Informer section. After you launch the website, you will notice an interface with all your installed programs. The button you will need to click is Advanced Uninstall. The window will enumerate all the additional installers and applications found in your system. Locate the games you want to uninstall and let the application do its job.